Well cementing method and apparatus



Oct. 15, 1940. Y n. -scARAMuccl 2,217,708y

' wsu.. cnu'EN'rING METHOD AND APPARATUS Filed May 8, 1939 Patented Oct.15, 1940 WELL CEDIENTING IVIETHOD AND APPARATUS Dorner Scaramucci,Norman, Oklaf, assignor to Oil Equipment Engineering Corporation,Oklahoma City, Okla.. a corporation of Oklahoma.

Application May 8, 1939, Serial No. 272,514

10 Claims.

The present invention relates to a well cementing method and apparatusfor practicing such a method. f

In the cementing of bore holes, such as oil 5 wells, a tubular casing isinserted in the hole with an annular space surrounding its outside. anddefined exteriorly by the formation of the drilled hole. To prevent theinltration of water, it is customary to seal the well by forcing cementdown the inside of the casing, out the bottom and up into the annularspace, until it has reached the desired position, where it is permittedto set. Due to fissures, veins and other irregularities in theformation, it is diiiicult to predict how high the crest of a givenquantity of cement will rise in the annular space surrounding the wellcasing. The location of this crest has been approximated by volumetricmeasurements, and more recently, ways have been devised for checking itsposition after the cement has been permitted to set and while it isstill giving off heat. In the prior art method which has been indicated,a thermometric device is lowered into the casing and temperaturereadings are taken at regular space intervals, so that-a.

diagram may be made of temperature versusL depth of the well, and thepoint at which the crest of the cement 'is located may be determined bynoting the inection of the diagram curve. While the method just outlinedis useful for determining the final position of the top of the cementlining, it does not provide any way of ascertaining the crest of anunset body of cement as it moves up the outside of the casing-i1,

35 If this latter observation is possible, pumping may be continueduntil the sealing has reached the necessary height.

In the practice of .the method of this invention, an exothermicsubstance which is capable o of emitting a relatively large quantity ofheat when it reacts with the well fiuid, is placed within the casingahead of the cement, so that it will be forced downwardly therewith andrise up the outside of the casing immediately above the unset cement.Several ways are contemplated 'for obtaining this result. A quantity ofsuitable heat-emitting substance can be mixed with the first portion ofthe cement slurry as it is pumped "ofementing plug which will contain aheatinto the well casing, or the chemical substance l casing immediatelyprior to the discharge of the lowermost portion of the unset cementslurry.

By the use of thermometric means within the well casing, it will bepossible to locate the crest of the fluid cement by observing the markedtemperature manifestation at only one point. This manifestation willoccur immediately due to the vigorous action of the added heat-emittingsubstance.

It will be apprehended, therefore, that a. general object of thisinvention is to provide a well I0 cementing method in which the.position of the crest of a moving body of cement can be determinedaccurately and controlled before the cement has begun to set.

Specifically, an object is the provision of ae l5 method in which aheat-emitting substance is added' to the initial portion of the body ofcement which is introduced into a well casing for sealing purposes.

A modified object is to provide a novel method of cementing whichincludes as cfstep the introduction of a separate exothermlc substanceinto a well casing immediately ahead of a. body of unset cement which isto be forced down said casing and up the outside thereof.

x Among the additional objects of the invention `is the provision of a.method in which unset cement is forced down a well casing and up thesides into a predetermined sealing position, which position `isaccurately located by thermometric measurements of the thermal eiectproduced by an exothermc substance at the crest ofthe unset cement. l

A further object is to. provide a. novel form emitting substance andpermit it to be introduced into the annular space surrounding the wellcasing immediately ahead of the cement slurry as it is forced upwardly.i

` A more complte understanding and appreciation of the objectsanddetails of this invention may be obtained fromthe following descriptionof the preferred practicof the method and the apparatus appurtenantthereto, taken in connection with the accompanying drawing, in which-Fig. 1 is a vertical section of an oil Well which includes a casing,cementing plugs, a body of unset cement, and a temperature measuringmeans; Fig. 2 is a similar section of the well, but shows the cementbody in a different relative position and indicates a device formeasuring the position of the temperature measuring means Within thecasing;

Fig. 3 is a diagrammatic representation of the temperature measuringmeans and the electric circuit which it involves; and

Fig. 4 is an enlarged, longitudinal section of a novel cementing plug.

For an illustration of the practice of this invention, reference is nowmade specically to Figs. 1 and 2 in which a continuous tubular casing Iis inserted in a bore hole so as to provide an annular space surroundingthe outside of lthe casing. At its'lower end, the casing string I8 isprovided with a guide shoe I2 of conventional form. For the purposeofcementing, a removable head and stuiing box I3 of conventional form isused. A lower cementing plug I4 and an upper cementing plug I6 arespaced by a body I8 of unset cement. As Will be understood by thosefamiliar with this art, the cement body I8 is being forced downwardlyinthe casing, I8 by means of fluid pressure on the upper cementing plugI6. A chemical substance 20,

' which will react vigorously with the water-bear ing well fiuid 22, isinserted as a layer between the bottom of the cement body I8 and the topof the lower cementing plug I4. One substance particularly suitable forthis purpose is calcium oxide which will be introduced in suillcientquantity to produce the desired thermal effect.

In Fig. 2, the downwardly moving cement body I8 has reached the bottomof the casing I0 and has flowed out through the ruptured lower plug I4and the shoe I2 and into the annular recess, which surrounds said.casing, to the height indicated. It is to be observed, that the chemicalthermometric coil 32 such as is indicated in Fig.

3, and the measuring cable 38 comprises a pair of insulated conductors33 and 34 leading from the coil 32 to a. battery 36, which is in serieswith an electrical current meter 38 and said coil. Ameasurement of thetemperature at the sounding weight 24 is obtained by the variation inresistance of the thermometric coil 32, which is shown at the meter 38.VThe meter 38 may be calibrated to read in degrees of temperature.

Generally, it is preferable to mix the chemical substance 20 with thefirst part of the cement body I8 that is pumped into the casing I8.However, Fig. 4 indicates another suitable means for placing thechemical substance at the rising crest of the cement body. The lowercementing plug |48, shown in this 'gure, has a large, longitudinalcentral bore 40 which is closed at its bottom end by a relatively thindiaphragm 42, which may be of rubber. The plug |48, which may be made ofwood, has suitable sealing washers 44, 46 and 48 attached to its bottomand top in the manner shown. Before the plug I4 is placed within thecasing i0, the bore 40 above the diaphragm 42 will be lled with thechemical substance 20. When the bottom plug I4 arrives at the shoe I2,the continued application of hydraulic pressure above it will cause thediaphragm 42 to rupture and discharge the heat-emitting substance 20through the shoe I2 and up the annular recess surrounding the casing I0.Since pressure is exerted on both the descending and ascending surfacesof the cement body I8, the crest-of the latter outside the casing I0will be directly beneath and substantially in contact with the chemicalsubstance 20.

By the present method, the crest of the fluid cement can be followedupwardly by keeping the sounding weight at a point of maximumtemperature, which point will be clearly defined adjacent theheat-emitting substance 20. Alternatively, the thermometric coil 32 maybe lowered to a measured position within the casing, and the arrival ofthe cement crest observed. It is customary to leave a substantialportion of the cement body I8 within the bottom of the casing I0 inorder to permit the operator to continue forcing the cement upwardlyoutside of said casing until it has reached a predetermined level and toprevent dilution. After the cement has set, the portion remaining in thebottom of the casing, the cementing plugs I4 and I6, and the shoe I2 canbe drilled out.

The chief advantage of the present method resides in the fact that thelocation of the cement can be accurately determined while it is still ina fluid state and subject to the control of an operator. By so doing, itis possible to obtain an eilicient lining instead of merely checking thelocation of a defective one, as is the case when measurements are takenafter the cement has set.

With the method of the present invention, the cementing operationbecomes a single one and all need .for logging, perforating,re-cementing and re-logging in the event of a cementing failure iscompletely eliminated; From an economic standpoint, there is a. greatsaving in the cost of the follow-up services which have been indicated.In new fields where time is paramount, the saving due tov lossinfshutdown time may amount to thousands of dollars.

It might be noted, incidentally, that in obviating the need forperforating, the danger of was shown by means such as thermometric'logging of the well after the cement had set. Since it is the commonpractice in the cementing of oil wells to add a retarding agent to thecement in order that it might be pumped a considerable distance intoposition before any set has taken place. it will be recognized that themethod herein described is peculiarly useful before any initial set ofthe cement, and isvnot' dependent upon an interval of hours or days,which is necessary where the heat emitted by the cement in setting isutilized to determine the ilnal positiom of the cement. In other words,mixed cement does not give off appreciable heat before the initial setperiod, and it is customary to delay the period of initial set in thecementing of oil Wells. Ordinarily, it requires from fifteen minutes toninety minutes for most cementing operations, i. e., mixing and pumpingdown the cement. In one instance, 1,500 sacks of cement were mixed andpumped down an 11,000-foot casing in fifty-two minutes. The set of thecement must, accordingly be retarded for this period at least.

Where the term cement is used in the foregoing specification, it isdirected primarily to the various mixes of Portland cement which areused for sealing oil wells, but it is to be understood that othercements may be found equally suitable and are .intended to be included.In

2. A method of cementing wells which includes' forcing a heat-liberatingsubstance down the. well adjacent the bottom of a body of cement, andutilizing the heat manifestation of the substance to determine theposition of the cement before it 3. The method of lining a bore holewith a sealing agent such as cement, comprising, introducing a casingstring into the bore hole so as to pro- A vide an annular space betweenitand the surface of the bore hole, inserting in the casing a substancewhich will liberate heat vigorously when it reacts with the uid in thebore hole, forcing the sealing agent upwardly into. said spaceimmediately behind the heat-liberating substance, and locating the crestof the sealing agent before it hardens by measuringrthe temperature inthe casing adjacent the heat-liberating substance.

4. The method of cementing wells comprising inserting a substance in awell casing which will produce a vigorous exothermic effect when-itreacts with a water-bearing fluid in the well. force ing a body of unsetcement down the casing adjacent the exothermic substance until it passesthrough an opening in the casing and rises to sealing position in theannular space between the casing and the formation, locating the crestof the cement by measuring the temperature within the casing adjacentthe exothermic substance which precedes the unset cement,` and stoppingthe movement of the unset cement When its crest has reached a desiredelevation.

5. The method of cementing wells comprising mixing with a small portionof unset cement a substance which will produce a vigorous exothermiceffect when it reacts with a water-bearing uid in the well, insertingthe thus mixed substance and cement in a Well casing, inserting a largeportion of unset cement in the casing behind the small portion, forcingthe whole body of unset cement down the casing until it passes outthrough an opening in the said casing and rises to sealing position inthe annular space between the casing and the formation, locating thecrest of the cement by measuring the temperature within the casingadjacent the exothermic substance which precedes the unset cement, andstopping the movement of the unset cement when its crest has reached adesired elevation.

6. An improved method of cementing oil wells comprising introducing intoa casing string in advance of a main body of cement slurry a substancewhich will react vigorously with the well fluid to produce a distinctexothermic eiect, forcing said substance and cement slurry down the`casing string and upwardly into the well bore space surrounding saidcasing, and Afollowing the crest of the upwardly rising cement slurry toits desired position by measuring the temperature within the casingopposite the exothermic substance.

7. The method of lining a bore hole with cementcomprising, introducing atubular casing into the bore hole so as to provide an annular spacebetween it and the surface of the bore hole, inserting in the casing alower cementing plug containing a substance which will liberate heatvigorously when it reacts with the fluid in the bore hole, releasing theheat-liberating substance from the plug when it reaches an opening inthe casing, forcing cement upwardly into s'aid space immediately behindthe heat-liberating substance, and

locating the crest of the cement before it sets by jacent theheat-liberating substance.

8. A cementing plug for oil wells comprising a frangible body member,said body member having a longitudinal bore therein, well casing sealingmeans secured to the top and bottom of said body measuring thetemperature inside the casing ady member, and a thinV diaphragm coveringthe lowe" end of the bore in the body member so as to provide a chambertherein which is open on the topside only.

9. A cementing plug for oil wells comprising a frangible body member,said body member having a longitudinal bore therein, well casing sealingmeans secured to the said body member, and a thin rubber diaphragmcovering the lower end of the bore in the body member so as to provide achamber therein which is open on the topside only.

10.I A cementing plug for oil frangible body member, said body memberhaving a longitudinal bore therein, well casing sealing means secured tothesaid body member, a thin rupturable diaphragm covering the lower endof the bore in the body member so as to provide a chamber therein whichis open on the topside only, and within the chamber a. chemicalsubstance which will liberate heat vigorously when mixed with well:fluid upon rupture of the diaphragm.

wells comprising a, J

, DOMER, SJARAMU CCI. @o

